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Discussion in 'Thumpers' started by neduro, Aug 16, 2008.
Not that we are impatient or anything like that
I've wondered about this too, watching Dakar footage of the RR bikes at speed in soft stuff. I have a 690 and it pretty much rides soft sand like my 300 XC (you want to be on the power to lighten the front). The Dakar racers seem to weight the front end when they stand; the back moves around, but the front seems planted. I think it may be more than just the trellis frame, but a combination of other parameters. Don't the RR's have long swing arms, longer wheel base, different rake and trail than a typical dirt bike chassis?
Ned, you mention how awesome the 690RR does in the sand compared to the XC4 based bike. How does it compare in the tight, technical stuff?
deposit has been put in for my own former rally spec 525!
now.... anyone still have the 660 tanks they'd like to sell? Or even the mecasystems tanks?
I know the person who have full Meca System kit laying in garage. Also 690RR and 660RR, but that's another story.
If You are really intersted, I can ask him about selling it
And here is my 576 SXS motor in 2005 EXC chassis. with a few mods. Love rally bikes, but I'm riding only 50km radius of my home and for longer trips I can rent a 98 Adv'R from my father.
Rally bike? Here is mine:
I loaned it to the Red Bull Museum in Salzburg, Austria. The fuel pump died, so I just left it there..
I'd think it'd be the other way. Trellis not as stiff so it can bend more. Ala the Ducati MotoGP bikes.
I'm no engineer. (obviously!) Nor have I ridden Ned's bike.
I decided to go over there and pick it up from them.... they tried calling you... no answer... they seemed to be giving it away
if you could ask him I would appreciate it!
In the first photo of the bike it looks like it has a different swing arm compared to the second photo and all the other 690rr's I've seen.
Is it different or are my eyes playing tricks on me ?
Uh... same bike same museum...
I kind of thought you would be posting this.. touche!
The trellis type of frame is usually much stiffer than the single backbone type. Designers tune the allowable deflection in an enduro bike for handling, that all goes out the window when you throw 35 l of fuel on it.
Yep realised that but I just wondered if the swing arm had been swapped.
It identical. The light angle is different, so the groove blends in.
They do have different/ longer swingarms and linkages to a 690 Enduro, and I think the geometry is somewhat different as well, but I'm not positive about that.
We rode some fairly technical stuff (here's a pic I took, the RR was already through this section):
and it works way better than it seems like it will, biggest issue was the wide skidplate.
In flowing sections, it was a weapon. The only shortcoming I had was in medium speed (~20mph) baby head rocks, where the rigidity cut the other way- the bike pinged off things where an enduro would have flowed through. It wasn't bad, just not as easy to ride, and that could be partly suspension as well.
Regarding the difference in deep sand, my theory is that when the front wheel is partly buried and the rider is at full gas, creating an enormous load on the frame, an enduro bike chassis noodles around a bit. This creates a weave that's hard to get rid of with suspension setup (I haven't been successful in doing so). In that situation, the rigidity of the trellis frame comes into play, and why the front end seems so much more planted.
The factory bikes from that era (Coma and Despres) have different trellis patterns to the customer bikes (like mine). So this is something that KTM know a lot about... more than they are telling!
Thanks Ned for your insight and reply. The factory does know stuff that old guys like me puzzle over. They make it look easy most of the time except last night when Dungy's air shock went flat. Fortunately he didn't try to race it.
The bike is this one, what are You really interested for? This man is serious and I don't wanna do just empty speaking! I know the bike was sold as stock EXC 525 and the rally kit is laying in garage.
I'd be interested in the front fairing, frame, and rally side tanks.